Laser ablation has been used in surgical procedures for treating various clinical conditions. Photoselective vaporization of the prostate (PVP) is a laser ablation surgery for treating an enlarged prostate (benign prostatic hyperplasia).
During a PVP surgery, a surgeon inserts an optical fiber into the urethra through a continuous flow cystoscope. A high-power green light laser beam is emitted through an optical fiber to vaporize and precisely remove enlarged prostate tissue. During the surgery, an irrigation fluid is provided into the bladder through a flow sheath in the cystoscope to maintain a clear field of vision, and to cool the laser optical fiber and surrounding tissues for preventing overheating of the bladder and prostate during the laser ablation of the prostate due to heat transfer. Because the tissue is vaporized and removed, a wide-open channel is created. The urine flow is improved and bothersome urinary symptoms are decreased.
PVP surgery is an effective and less invasive alternative to older, more traditional methods of removing prostate obstructions. After the surgery, most patients are released in less than 24 hours, in many cases without a catheter, and recovery time is shorter. Because PVP surgery vaporizes tissue rather than cutting or resecting it, there's generally less blood loss, particularly beneficial to men who have blood-clotting conditions or those who take blood thinners. In the past ten years, thousands of PVP procedures have been successfully performed to treat patients who suffer from symptoms of benign prostatic hyperplasia.
However, since PVP surgery is relatively new, side effects and potential complications and risks due to exposure of the surrounding tissue to elevated temperature over extended period time of the ablation procedure have not been fully studied or understood. It is assumed that the bladder cavity serves as a protective heat sink that absorbs and dissipates the excessive thermal energy generated by the laser ablation surgery. It is known that during the PVP procedure, the temperature inside the bladder rises substantially even in the presence of the irrigation fluid. After applying high energy GreenLight laser to the prostate continuously for a period of time, such as 5-20 minutes, effluent exiting the bladder through the fluid outlet of cystoscope becomes hot. Sometimes, the ablation process takes more than 60 minutes, therefore, the temperature inside the bladder rises to such an extent under which the bladder may incur a thermal injury. It has been observed that heat transfer due to a prolonged PVP procedure can result in immersion scalding injury to adjacent non-target tissue.
Commonly, an irrigation is provided using a sterile saline solution contained in a flexible bag, which is connected to the continuous flow cystoscope through a tubing. The flow rate is manually controlled by the surgeon and surgical staff, and the bag may need to be replaced when the solution runs out. When the flow rate is insufficient for heat dissipation, the temperature inside the bladder could rise to the degree that could cause a thermal injury to the bladder. Burns of the inner lining of the bladder has been observed following PVP surgery when the irrigation fluid is insufficient and/or transiently not provided due to mechanical problem or operation error, which resulted in painful post-surgery complications. Irreversible changes and the severity of epithelial and deep tissue injury can be a function of the temperature to which the tissue is exposed to and duration of the exposure.
Currently, laser ablation equipment used for PVP surgery operates independently from the management of irrigation of the bladder. No device is available for monitoring or controlling the temperature in the bladder for the PVP surgery. Management of the irrigation fluid to compensate for the heating to the bladder during the surgery is provided manually based on surgeon's observation and experiences. This presents a significant risk to patient safety due to a potential human error or mechanical failure in managing the irrigation fluid.
Therefore, there is a strong need for an improved laser ablation surgical system and safety measurement that overcomes the above mentioned deficiencies.